1. Field of the Invention
This invention relates to apparatus for the accurate determination of velocity of a gas in a gas supply duct, more particularly so that gas flow rate may be maintained uniform between the individual ducts supplying gas to their respective plenum chambers for delivery to quenching chambers for the quenching of synthetic filaments produced by a melt-spinning process.
2. The Prior Art
Each spinning position in a melt-spinning process has a quenching chamber to which gas is supplied through a plenun chamber from a supply duct. See, for example, U.S. Pat. No. 3,999,910 to Pendlebury et al., hereby incorporated by reference. A plurality of positions are normally located in side-by-side relationship with their gas supply ducts fed by a header. Unfortunately, the supply ducts are not of uniform length, and some have elbows and/or butterfly valves therein, which create turbulence in the gas supply duct. A single point pitot tube has been used to measure the gas velocity in the duct just prior to entry to the plenum chamber. The velocity measurement is then converted to determine the gas flow rate in cubic feet per minute. If the velocity measurement is not representative of the gas velocity in the duct, however, an inaccurate determination of flow rate will result, and an attempt at maintaining the flow rates uniform on a plurality of positions will fail. The result is seen in differing yarn physicals for the process product. It was therefore necessary to devise apparatus which would make more accurate the determination of the gas velocity. In a duct or pipe of straight length greater than ten times the inside diameter of the duct prior to measurement, a differential pressure cell combined with an orifice plate will suffice. However, when the straight length is ten times the inside diameter of the duct or less prior to measurement, this combination is insufficient.
Prior art believed to be pertinent to the examination of the present invention is U.S. Pat. Nos. 4,130,017 to Benedict et al., 3,733,898 to Yamamoto et al., and 3,636,765 to Brown, all of which are hereby incorporated by reference.